I am not sure what the chemical taste is, but some think it has to do with the nicotine base. It seems that a vendor either has it, or doesn't. Sometimes it will go away with steeping. I avoid certain vendors because of that taste (or even rumors of that taste). Some people say Halo has the best juices, pure clean flavor, better than any others. Some say there juices taste like bug spray. I tried some of their Tribecca and it was like spraying mosquito repellent into my mouth. I easily gave the bottle away in PIF. Some people love it, I didn't. Johnson Creek is another one I can't stand, yet others rave about.
Some vendors have a "signature" base, where all their juices have that same background taste. Sometimes it is a good background flavor. KickBassVapor has one of those. I can taste butter in everyone of their flavors. This works great with their Rice Krispity Treats and Sugar Cookie, but not as good in their Marionberry (Raspberry) Ice Cream.
Many vendor's tobacco flavors are (to me) nasty. When was tobacco the flavor of tin? They all tasted like licking a tin shed. Vermillion Rivers and Quicknic have a woody tobacco flavor, more like a campfire. And BackWoodsBrew has the best I have tried (after a two week steep) in Casablanca.
Kriptonite is Goodejuice's best (most famous) flavor. Good stuff. Nick is a great vendor, and if you have any problems he will bend over backwards to help you out. I also have heard he goes to Chicago vape meets sometimes.
For good fruits you can't beat Copper Creek. They are 100% natural (some juices), so it won't taste medicinal. You can ask for the Watermelon. It is a new flavor and suppose to be awesome. House Blend is a good flavor.
And of course, your milage may vary.
I ordered some Ms T's but shes pretty $$$ too. (blueberry and the strawberry cheesecake, snickerdoodle and her twinkie one) I am super excited to try quicknic as they are so close I could almost drive up there 
